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Re: issue-base-param

From: Chimezie Ogbuji <ogbujic@ccf.org>
Date: Tue, 17 Apr 2007 15:57:35 -0400
To: "Jeremy Carroll" <jjc@hpl.hp.com>
cc: "GRDDL Working Group" <public-grddl-wg@w3.org>
Message-ID: <1176839855.26300.17.camel@otherland>

Just a few clarifications to my last email (in retrospect)

On Tue, 2007-04-17 at 13:51 -0400, Chimezie Ogbuji wrote: 
> With XSLT 1.0, we only have a problem if there isn't an xml:base attribute in the document or there is 
> an xml:base which is not absolute (as Jeremy pointed out).  If there isn't an xml:base attribute, we 
> supply the baseURI of the source document as the “the Base URI of the document entity“.  This is consistent 
> with our base-param-issue resolution:
> 
> [[[
> RESOLVED: Given that a base URI parameter is a parameter whose value is the base URI of the source document, 
> the WG RESOLVES not to define a base URI parameter for transforms.  
> ]]]

The language of the resolution is a bit misleading (or at least
confusing), but with a few replacements becomes consistent with XSLT.
In particular if you remove the word 'parameter' wherever you see it
then this removes the confusion with the notion of an xsl:param (an
XPath variable binding).  This is different from providing the URI of
the document entity as an API "parameter".

In at least two XSLT 1.0 implementations that I know of (Saxon [1] and
4Suite [2]) there is an implicit assumption that the source uri is the
URI of the document entity (so it is an implicit API parameter).

> > Do we respect xml:base attributes or not? 
> 
> If we cite XML Base normatively then it requires that we do.

If you were talking about the interpretation of xml:base by our XPath
expressions, then I was mistaken.  XML Base would only give a 'fallback'
definition for the base URI of the document entity but no more.  Since
XPath has it's own abstract model (which XML infoset can be mapped *to*)
we would not be able to support XML Bases resolution with respect to an
arbitrary element as this requires that the nodes in the model each have
a notion of a Base URI which can be 'inherited' down the hierarchy.

So, any use of xml:base in a GRDDL source document (by GRDDL source
document I mean the document against which the XPath expressions in the
normative green boxes are evaluated) would be disregarded and the XML
Base / RFC 2396 chain would begin with the assumption that there was no
base URI embedded in the document's content:

4.1 Relation to RFC 2396
        
     2. The base URI is that of the encapsulating entity (message,
        document, or none).
        
     3. The base URI is the URI used to retrieve the entity.
        
     4. The base URI is defined by the context of the application.
        

4.2 Granularity of base URI information

  3. the base URI of the document entity or external entity containing
the element.


[1] http://saxon.sourceforge.net/saxon7.2/using-xsl.html
[2] http://4suite.org/docs/CoreManual.xml#base_URIs

-- 
Chimezie Ogbuji
Lead Systems Analyst
Thoracic and Cardiovascular Surgery
Cleveland Clinic Foundation
9500 Euclid Avenue/ W26
Cleveland, Ohio 44195
Office: (216)444-8593
ogbujic@ccf.org


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Received on Tuesday, 17 April 2007 20:21:52 GMT

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